Pervasive CpG suppression in animal mitochondrial genomes.

All available complete mitochondrial genomes (21 species) are evaluated for dinucleotide over- and under-representation. The CpG dinucleotide is pervasively under-represented in all animal mitochondria, but it is of variable relative abundance in fungal, protist, and plant mitochondrial genomes. Interpretations and hypotheses are considered relative to mitochondrial genome organization, methylation, structural specificities, directed mutation, and evolutionary events. In particular, our results support Mycoplasma capricolum or a close relative as the most likely bacterial ancestor of the mitochondria.